1. Field of the Invention
This invention relates to the field of medical diagnosis and, more specifically, to the use of a catheter to illuminate human body tissue in order to generate reflected radiation therefrom, and to the use of interferometer apparatus to analyze the reflected radiation.
2. Description of Related Art
Guidewire catheters are generally known in the art. U.S. Pat. No. 4,545,390 describes a catheter having a relatively long wire having a proximal end, and a distal end. A relatively short helically wound spring is connected to the wire's distal end, and the wire's distal end is bendable to retain a curve, and is sufficiently flexible to follow a blood vessel. The wire is sufficiently torsionally rigid to transmit angular rotation from the proximal end to the distal end. In U.S. Pat. No. 4,554,929, a safety wire interconnects the wire and the coil. In U.S. Pat. No. 4,619,274, a catheter core element decreases in diameter from its proximal end to its distal end, and a helical coil has a diameter that decreases toward its distal end, the coil being formed of a wire whose diameter decrease, with the wire's larger diameter being at the proximal end. In U.S. Pat. No. 4,721,117, a tubular heat shrinkable jacket covers the wire. In U.S. Pat. No. 4,748,986, the catheter wire has a tapered intermediate portion, and a flattened distal portion. A coil surrounds the wire, and a safety wire interconnects the wire and the coil.
Catheters containing optical fibers are generally known in the art. U.S. Pat. No. 4,648,892 describes a catheter having an optical shield for the distal end of the catheter. In U.S. Pat. No. 4,669,465, an interlock is provided to prevent operation of a laser until the end of a beam transmitting fiber extends beyond the distal end of the catheter. In U.S. Pat. No. 4,669,467, the ends of a pack of optical fibers are stressed in order to mix the modes of the optical fibers.
It is known to analyze radiation that is received from tissue as a result of illumination of the tissue by the use of a catheter. U.S. Pat. No. 4,718,417 describes illuminating tissue with radiation that is generally in the 480 nm range, and then analyzing reflected radiation, generally in the range of 520 to 610 nm, in order to distinguish between healthy tissue and other material, such as plaque. In U.S. Pat. No. 5,104,392, the device operates to continue to ablate a tissue mass until a characteristic reflection is no longer received therefrom. In U.S. Pat. No. 5,106,387, a catheter is used to illuminate a tissue mass to thereby induce fluorescence of the tissue. The returned fluorescence is then analyzed in order to diagnose the tissue mass.
The above patents are incorporated herein by reference for the purpose of indicating the background of the invention, and illustrating the state of the art. While these devices are generally satisfactory for their stated purposes, a need remains in the art for an improved unitary guidewire/optical catheter, and improved apparatus for use in analyzing radiation that is reflected from tissue as a result of radiation from the unitary catheter.